/*
 * Copyright 2012-2023 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.boot.web.embedded.tomcat;

import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.BiConsumer;
import java.util.stream.Collectors;

import javax.naming.NamingException;

import org.apache.catalina.Container;
import org.apache.catalina.Context;
import org.apache.catalina.Engine;
import org.apache.catalina.Lifecycle;
import org.apache.catalina.LifecycleException;
import org.apache.catalina.LifecycleState;
import org.apache.catalina.Service;
import org.apache.catalina.connector.Connector;
import org.apache.catalina.startup.Tomcat;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.naming.ContextBindings;

import org.springframework.boot.web.server.GracefulShutdownCallback;
import org.springframework.boot.web.server.GracefulShutdownResult;
import org.springframework.boot.web.server.PortInUseException;
import org.springframework.boot.web.server.Shutdown;
import org.springframework.boot.web.server.WebServer;
import org.springframework.boot.web.server.WebServerException;
import org.springframework.util.Assert;

/**
 * {@link WebServer} that can be used to control a Tomcat web server. Usually this class
 * should be created using the {@link TomcatReactiveWebServerFactory} or
 * {@link TomcatServletWebServerFactory}, but not directly.
 *
 * @author Brian Clozel
 * @author Kristine Jetzke
 * @since 2.0.0
 */
public class TomcatWebServer
        implements WebServer {

    private static final Log logger = LogFactory.getLog(TomcatWebServer.class);

    private static final AtomicInteger containerCounter = new AtomicInteger(-1);

    private final Object monitor = new Object();

    private final Map<Service, Connector[]> serviceConnectors = new HashMap<>();

    private final Tomcat tomcat;

    private final boolean autoStart;

    private final GracefulShutdown gracefulShutdown;

    private volatile boolean started;

    /**
     * Create a new {@link TomcatWebServer} instance.
     *
     * @param tomcat the underlying Tomcat server
     */
    public TomcatWebServer(Tomcat tomcat) {
        this(tomcat, true);
    }

    /**
     * Create a new {@link TomcatWebServer} instance.
     *
     * @param tomcat    the underlying Tomcat server
     * @param autoStart if the server should be started
     */
    public TomcatWebServer(Tomcat tomcat,
                           boolean autoStart) {
        this(tomcat, autoStart, Shutdown.IMMEDIATE);
    }

    /**
     * Create a new {@link TomcatWebServer} instance.
     *
     * @param tomcat    the underlying Tomcat server
     * @param autoStart if the server should be started
     * @param shutdown  type of shutdown supported by the server
     * @since 2.3.0
     */
    public TomcatWebServer(Tomcat tomcat,
                           boolean autoStart,
                           Shutdown shutdown) {
        Assert.notNull(tomcat, "Tomcat Server must not be null");
        this.tomcat = tomcat;
        this.autoStart = autoStart;
        this.gracefulShutdown = (shutdown == Shutdown.GRACEFUL) ? new GracefulShutdown(tomcat) : null;
        initialize();
    }

    private void initialize() throws WebServerException {
        logger.info("Tomcat initialized with " + getPortsDescription(false));
        synchronized (this.monitor) {
            try {
                addInstanceIdToEngineName();

                Context context = findContext();
                context.addLifecycleListener((event) -> {
                    if (context.equals(event.getSource()) && Lifecycle.START_EVENT.equals(event.getType())) {
                        // Remove service connectors so that protocol binding doesn't
                        // happen when the service is started.
                        removeServiceConnectors();
                    }
                });

                disableBindOnInit();

                // Start the server to trigger initialization listeners
                this.tomcat.start();

                // We can re-throw failure exception directly in the main thread
                rethrowDeferredStartupExceptions();

                try {
                    ContextBindings.bindClassLoader(context, context.getNamingToken(), getClass().getClassLoader());
                } catch (NamingException ex) {
                    // Naming is not enabled. Continue
                }

                // Unlike Jetty, all Tomcat threads are daemon threads. We create a
                // blocking non-daemon to stop immediate shutdown
                startNonDaemonAwaitThread();
            } catch (Exception ex) {
                stopSilently();
                destroySilently();
                throw new WebServerException("Unable to start embedded Tomcat", ex);
            }
        }
    }

    private Context findContext() {
        for (Container child : this.tomcat.getHost().findChildren()) {
            if (child instanceof Context context) {
                return context;
            }
        }
        throw new IllegalStateException("The host does not contain a Context");
    }

    private void addInstanceIdToEngineName() {
        int instanceId = containerCounter.incrementAndGet();
        if (instanceId > 0) {
            Engine engine = this.tomcat.getEngine();
            engine.setName(engine.getName() + "-" + instanceId);
        }
    }

    private void removeServiceConnectors() {
        doWithConnectors((service, connectors) -> {
            this.serviceConnectors.put(service, connectors);
            for (Connector connector : connectors) {
                service.removeConnector(connector);
            }
        });
    }

    private void disableBindOnInit() {
        doWithConnectors((service, connectors) -> {
            for (Connector connector : connectors) {
                Object bindOnInit = connector.getProperty("bindOnInit");
                if (bindOnInit == null) {
                    connector.setProperty("bindOnInit", "false");
                }
            }
        });
    }

    private void doWithConnectors(BiConsumer<Service, Connector[]> consumer) {
        for (Service service : this.tomcat.getServer().findServices()) {
            Connector[] connectors = service.findConnectors().clone();
            consumer.accept(service, connectors);
        }
    }

    private void rethrowDeferredStartupExceptions() throws Exception {
        Container[] children = this.tomcat.getHost().findChildren();
        for (Container container : children) {
            if (container instanceof TomcatEmbeddedContext embeddedContext) {
                TomcatStarter tomcatStarter = embeddedContext.getStarter();
                if (tomcatStarter != null) {
                    Exception exception = tomcatStarter.getStartUpException();
                    if (exception != null) {
                        throw exception;
                    }
                }
            }
            if (!LifecycleState.STARTED.equals(container.getState())) {
                throw new IllegalStateException(container + " failed to start");
            }
        }
    }

    private void startNonDaemonAwaitThread() {
        Thread awaitThread = new Thread("container-" + (containerCounter.get())) {

            @Override
            public void run() {
                TomcatWebServer.this.tomcat.getServer().await();
            }

        };
        awaitThread.setContextClassLoader(getClass().getClassLoader());
        awaitThread.setDaemon(false);
        awaitThread.start();
    }

    @Override
    public void start() throws WebServerException {
        synchronized (this.monitor) {
            if (this.started) {
                return;
            }

            try {
                addPreviouslyRemovedConnectors();
                Connector connector = this.tomcat.getConnector();
                if (connector != null && this.autoStart) {
                    performDeferredLoadOnStartup();
                }
                checkThatConnectorsHaveStarted();
                this.started = true;
                logger.info(getStartedLogMessage());
            } catch (ConnectorStartFailedException ex) {
                stopSilently();
                throw ex;
            } catch (Exception ex) {
                PortInUseException.throwIfPortBindingException(ex, () -> this.tomcat.getConnector().getPort());
                throw new WebServerException("Unable to start embedded Tomcat server", ex);
            } finally {
                Context context = findContext();
                ContextBindings.unbindClassLoader(context, context.getNamingToken(), getClass().getClassLoader());
            }
        }
    }

    String getStartedLogMessage() {
        return "Tomcat started on " + getPortsDescription(true) + " with context path '" + getContextPath() + "'";
    }

    private void checkThatConnectorsHaveStarted() {
        checkConnectorHasStarted(this.tomcat.getConnector());
        for (Connector connector : this.tomcat.getService().findConnectors()) {
            checkConnectorHasStarted(connector);
        }
    }

    private void checkConnectorHasStarted(Connector connector) {
        if (LifecycleState.FAILED.equals(connector.getState())) {
            throw new ConnectorStartFailedException(connector.getPort());
        }
    }

    private void stopSilently() {
        try {
            stopTomcat();
        } catch (LifecycleException ex) {
            // Ignore
        }
    }

    private void destroySilently() {
        try {
            this.tomcat.destroy();
        } catch (LifecycleException ex) {
            // Ignore
        }
    }

    private void stopTomcat() throws LifecycleException {
        if (Thread.currentThread().getContextClassLoader() instanceof TomcatEmbeddedWebappClassLoader) {
            Thread.currentThread().setContextClassLoader(getClass().getClassLoader());
        }
        this.tomcat.stop();
    }

    private void addPreviouslyRemovedConnectors() {
        Service[] services = this.tomcat.getServer().findServices();
        for (Service service : services) {
            Connector[] connectors = this.serviceConnectors.get(service);
            if (connectors != null) {
                for (Connector connector : connectors) {
                    service.addConnector(connector);
                    if (!this.autoStart) {
                        stopProtocolHandler(connector);
                    }
                }
                this.serviceConnectors.remove(service);
            }
        }
    }

    private void stopProtocolHandler(Connector connector) {
        try {
            connector.getProtocolHandler().stop();
        } catch (Exception ex) {
            logger.error("Cannot pause connector: ", ex);
        }
    }

    private void performDeferredLoadOnStartup() {
        try {
            for (Container child : this.tomcat.getHost().findChildren()) {
                if (child instanceof TomcatEmbeddedContext embeddedContext) {
                    embeddedContext.deferredLoadOnStartup();
                }
            }
        } catch (Exception ex) {
            if (ex instanceof WebServerException webServerException) {
                throw webServerException;
            }
            throw new WebServerException("Unable to start embedded Tomcat connectors", ex);
        }
    }

    Map<Service, Connector[]> getServiceConnectors() {
        return this.serviceConnectors;
    }

    @Override
    public void stop() throws WebServerException {
        synchronized (this.monitor) {
            boolean wasStarted = this.started;
            try {
                this.started = false;
                if (this.gracefulShutdown != null) {
                    this.gracefulShutdown.abort();
                }
                removeServiceConnectors();
            } catch (Exception ex) {
                throw new WebServerException("Unable to stop embedded Tomcat", ex);
            } finally {
                if (wasStarted) {
                    containerCounter.decrementAndGet();
                }
            }
        }
    }

    @Override
    public void destroy() throws WebServerException {
        try {
            stopTomcat();
            this.tomcat.destroy();
        } catch (LifecycleException ex) {
            // Swallow and continue
        } catch (Exception ex) {
            throw new WebServerException("Unable to destroy embedded Tomcat", ex);
        }
    }

    private String getPortsDescription(boolean localPort) {
        StringBuilder description = new StringBuilder();
        Connector[] connectors = this.tomcat.getService().findConnectors();
        description.append("port");
        if (connectors.length != 1) {
            description.append("s");
        }
        description.append(" ");
        for (int i = 0; i < connectors.length; i++) {
            if (i != 0) {
                description.append(", ");
            }
            Connector connector = connectors[i];
            int port = localPort ? connector.getLocalPort() : connector.getPort();
            description.append(port).append(" (").append(connector.getScheme()).append(')');
        }
        return description.toString();
    }

    @Override
    public int getPort() {
        Connector connector = this.tomcat.getConnector();
        if (connector != null) {
            return connector.getLocalPort();
        }
        return -1;
    }

    private String getContextPath() {
        return Arrays.stream(this.tomcat.getHost().findChildren())
                .filter(TomcatEmbeddedContext.class::isInstance)
                .map(TomcatEmbeddedContext.class::cast)
                .map(TomcatEmbeddedContext::getPath)
                .collect(Collectors.joining(" "));
    }

    /**
     * Returns access to the underlying Tomcat server.
     *
     * @return the Tomcat server
     */
    public Tomcat getTomcat() {
        return this.tomcat;
    }

    @Override
    public void shutDownGracefully(GracefulShutdownCallback callback) {
        if (this.gracefulShutdown == null) {
            callback.shutdownComplete(GracefulShutdownResult.IMMEDIATE);
            return;
        }
        this.gracefulShutdown.shutDownGracefully(callback);
    }

}
